1. Field of the Invention
The object of the present invention is a set of lighting devices with light-emitting diodes, the acronym for which is LEDs, able to generate an adaptive light beam. A lighting device, generally, is an optical unit able to generate a light beam, based on one optical module or several optical modules, and intended to be integrated in a headlight device.
2. Description of the Related Art
The field of the invention is in general terms that of motor vehicle headlights. In this field, various types of conventional headlights are known, among which there are primarily:
side lights with low intensity and range;
low or dipped beam lights, of higher intensity and a range on the road of around 80 meters, which are used essentially at night and where the distribution of the light beam is such that it makes it possible not to dazzle the driver of a vehicle being passed; the light beams of the dipped beam type differ with the type of traffic, on the left or on the right, in which they are used;
high beam lights of the long range type where the area of vision on the road is around 600 meters, and which must be switched off when passing another vehicle in order not to dazzle its driver;
fog lights; and
a type of improved headlight, referred to as dual function, which combines the functions of dipped beam lights and high beam lights.
The conventional lighting devices that have just been mentioned, more particularly those that are used as dipped beams, produce light beams that are open to improvement when they are used under certain conditions. Thus, for example, when a vehicle is entering a bend, the headlights continue to illuminate straight in front of them whereas it would be more judicious to orient the light beams in the direction of the bend being taken. This is why, in addition to the conventional main headlight functions, particularly dipped beam and main beam, various improvements have gradually appeared.
Thus, elaborate functions have been seen, referred to as advanced functions, or AFS (“Advanced Front lighting System” in English meaning advanced front lighting system), among which there are also found particularly, directly relating to the invention, a so-called DBL function (“Dynamic Bending Light” in English meaning movable bending light, called “code virage” in French), which produces an orientable headlight, also referred to as a movable beam lighting device: such a lighting device is able to modify the orientation of a light beam produced by a lighting device so that, when the vehicle is entering a bend, the road is illuminated in an optimum fashion, following the geometry of the road.
In order to fulfill such a function, a first known technique consists of making the global beam of the lighting device movable by virtue of an actuator controlling the pivoting, at least partial, of the lighting device according to information coming from the vehicle, for example by means of a steering wheel angle sensor.
For all the headlights and side lights that have just been mentioned, conventionally, light sources of the halogen lamp or discharge lamp type are used. But for a few years now automotive equipment suppliers have proposed the use of light-emitting diodes, also called LEDs; this use for example relates to indicator lights or rear lights.
Light-emitting diodes offer a certain number of advantages. First of all, for a long time, it has been known that this type of diode does not radiate omni-directionally but radiates in a half space opposite to the substrate that supports the p-n junction of the diode in question; thus, by using a more directive radiation than halogen or discharge lamps, the quantity of energy lost is less. Next these diodes were recently improved in terms of radiation intensity. In addition the diodes emit radiation, for a long time in the red range, but now also particularly in white and orange, which increases their field of possible uses. The quantity of heat that they give off is relatively limited but a certain number of constraints, relating to the dissipation of heat, remains high in the case of power LEDs. Lastly, LEDs consume less energy, even at equal intensity of radiation, than discharge lamps or halogen lamps; they are compact and their particular shape offers novel possibilities for producing and arranging the complex surfaces that are associated with them, particularly when arranging them on electronic media of the flexible type.
In addition, with a general aim of making driving more comfortable in terms of visibility, dual function headlight devices are used; in the dual function optical modules of these headlight devices, the dipped beam function automatically switches to the high beam function and vice versa, the switching being dependent on the traffic conditions. With vehicles equipped with such dual function modules, the procedure starts by searching for the presence of a vehicle liable to be dazzled by using the high beam function. If no vehicle is detected, the high beam function is automatically activated. As soon as the presence of a vehicle is detected, the high beam function is automatically de-activated and the vehicle equipped with the dual function headlight again projects a light beam of the dipped beam type.
In practice the threshold value above which the absence of a detected vehicle authorizes switching over to the high beam function is roughly 600 metres. As soon as a vehicle is detected at less than 600 meters from the equipped vehicle, it is the dipped beam function which is activated. However this function only ensures satisfactory lighting to a distance of about 80 meters in the central section of the road, and 150 meters on the verges of the road along which the vehicle is travelling (that is to say the right verge with respect to right-hand traffic); the lighting thus being projected primarily on the right side of the road in the case of right-hand traffic, the left side of the road is substantially less illuminated. Thus, there exists many traffic configurations, in which the first vehicle liable to be dazzled is located more than 100 meters and less than 600 meters away from the equipped vehicle, for which the road lighting could be optimized, however without dazzling the driver of any another vehicle.
Thus, various solutions are proposed allowing the range of the beam to be adapted according to an estimated distance at which the vehicle being passed or followed is situated. Progressive light beams are then spoken of. Although these solutions may be satisfactory in terms of optimizing the range of the light beam, this is not the case if the side lighting of the road that is proposed is considered.
Thus, in the state of the art, solutions to cut off a global light beam emitted by a vehicle in various adjacent angular portions, each portion corresponding to an angular segment of the global beam are also proposed. Therefore, if the vehicle being passed or followed is present in a portion considered, an optimized global light beam would consist in rendering only the portion considered of the global light beam not dazzling. Selective light beams are then spoken of. A non-dazzling portion means an angular segment of the global light beam in which the beam is concentrated only under the horizontal when it reaches, or before reaching, the vehicle being followed or passed.
However solutions proposed in the state of the art for producing selective light beams in lighting devices also able to generate a light beam of the dipped beam type use all of the mechanical solutions including movable masks, producing variable cutoff lines depending on their positioning. Such devices, which are frequently in demand, encounter problems of reliability, particularly over the lifespan of the lighting device.